In the past decade, nanohybrid materials of carbon nanotubes with metal or metal oxide nanoparticles have been received extensive attention, which can be used in various applications such as gas sensors, supercapacitor electrodes, catalyst supports, and antimicrobial therapies. To enhance the efficacies of carbon nanotubes, dendrimers, which encapsulated Au nanoparticle, for example, have been adhered on the surface of multiwalled carbon nanotubes (MWCNTs) via the electrostatic attraction between the positively charged dendrimers and the negatively charged surface of MWCNTs (Herrero et al., ACS Nano 2010, 4(2), 905-912). However, hybrids constructed by non-covalent bonds might be affected by the external conditions like temperature, pH and additives and the attraction between the components might be released from such hybrids, depending on a variation of conditions. On the other hand, covalently functionalized dendrimers on MWCNTs as scaffolds have been utilized for in-situ immobilization of metal and metal oxide nanoparticles on them (Lu et al., Phys. Chem. C 2007, 111, 2416; and Lu et al., J. Phys. Chem. C 2007, 111, 8459). However, the in-situ synthesized metal nanoparticles have inhomogeneously distributed on the MWCNTs modified with dendrimers, which may decrease the desired efficacies of the MWCNTs. Therefore, a procedure to accomplish a uniform attachment of nanoparticles on carbon nanotubes is desired.
Among the various applications of carbon nanotubes, for example, carbon nanotube (CNT)/metal nanoparticle hybrid-modified electrodes have been developed for uses as fuel-cell catalyst and biosensor. For example, electrocatalysts for direct methanol fuel cell (DMFC) were prepared by electrodeposition of platinum nanoparticles (PtNPs) on MWCNT/Nafion and single walled carbon nanotube (SWCNT)/Nafion electrodes using Nafion as binder (Wu et al., J. Power Sources 2007, 174, 148-158); however, the preparation technique requires the costly and special equipment. In addition, a Pt-CNT/glucose biosensor was also developed by incorporation of glucose oxidase (GOx) on a Pt-CNT electrode using a Ptnano/SiO2 composite matrix as a binder; however, its stability after the storage for a few days decreased due to the release of GOx which is not incorporated within the Ptnano/SiO2 composite matrix (Yang et al., Biosensors and Bioelectronics 2006, 21, 1125-1131). Therefore, there is still a need to have a simple and low-cost method to prepare an effective electrode, which particularly reveals high durability, reactivity and stability and is useful in, for example, electrochemical sensing systems.